Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.

The distribution of electrons in various shells for the first eighteen elements follows a set of rules known as the Aufbau principle, the Pauli Exclusion Principle, and Hund's Rule. Here are the summarized rules:

1. Aufbau Principle: This rule states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. In other words, electrons fill up the lowest energy level first, then move to the next level.

2. Pauli Exclusion Principle: According to this principle, an atomic orbital may describe at most two electrons. To occupy the same orbital, two electrons must have opposite spins; one spins clockwise and the other counterclockwise.

3. Hund's Rule: This rule states that electrons will occupy an empty orbital in the same subshell before they pair up in the same orbital. This means that if there are two or more orbitals of the same energy (degenerate orbitals), one electron goes into each until all are half-full.

The distribution of electrons for the first eighteen elements (Hydrogen to Argon) would be as follows:

1. Hydrogen (1): 1s¹
2. Helium (2): 1s²
3. Lithium (3): 1s² 2s¹
4. Beryllium (4): 1s² 2s²
5. Boron (5): 1s² 2s² 2p¹
6. Carbon (6): 1s² 2s² 2p²
7. Nitrogen (7): 1s² 2s² 2p³
8. Oxygen (8): 1s² 2s² 2p⁴
9. Fluorine (9): 1s² 2s² 2p⁵
10. Neon (10): 1s² 2s² 2p⁶
11. Sodium (11): 1s² 2s² 2p⁶ 3s¹
12. Magnesium (12): 1s² 2s² 2p⁶ 3s²
13. Aluminum (13): 1s² 2s² 2p⁶ 3s² 3p¹
14. Silicon (14): 1s² 2s² 2p⁶